The parathyroid glands are four pea-sized glands located on the thyroid gland in the neck. Occasionally, a person is born with one or more of the parathyroid glands embedded in the thyroid, the thymus, or elsewhere in the chest. In most such cases, however, the glands function normally. Though their names are similar, the thyroid and parathyroid glands are entirely separate glands, each producing distinct hormones with specific functions. The parathyroid glands secrete parathyroid hormone (PTH), a substance that helps maintain the correct balance of calcium and phosphorous in the body. PTH regulates release of the calcium from bone, absorption of calcium in the intestine, and excretion of calcium in the urine. When the amount of calcium in the blood falls too low, the parathyroid glands secrete just enough PTH to restore the balance.